1. Field of the Invention
This invention relates to a semiconductor device with no base member and a method of manufacturing the semiconductor device.
2. Description of the Related Art
When a semiconductor chip is bonded to a circuit substrate, if the pitch of external connecting terminals of the semiconductor chip is short, it is difficult to perform direct flip-chip packaging. In such a case, the following packaging method is employed. A semiconductor chip is generally mounted on a stacked circuit substrate, called an interposer, to configure a semiconductor device, which is then bonded to a circuit substrate. Jpn. Pat. Appln. KOKAI Publication No. H9-36172 discloses a typical example of a semiconductor device where a semiconductor chip is mounted on an interposer. In the semiconductor device of such a prior art, the interposer includes a double-sided wiring structure wiring substrate of which interconnections provided on the upper surface of the substrate and the interconnections provided on the underside of the substrate are connected through vertical conducting parts. On the upper layer interconnections of the interposer, a semiconductor chip is mounted by the face-down method. On the underside of the lower layer interconnections of the interposer, there are provided a plurality of solder balls. Then, the solder balls are bonded to a circuit substrate by a suitable method, such as reflow techniques.
A semiconductor device described in the prior document has the following problem. Since a relatively expensive interposer having a double-sided wiring structure with vertical conducting parts is used, this leads to high production costs and makes the overall device thicker.